Hydrofoils



April 1963 F. B. s. GRIMSTON 3,087,452

HYDROFOILS Filed Feb. 7, 1961 Patented Apr. 39, W63

3,637,452 HYEROFOILS Francis Brian Sylvester Grimston, Royal Thames Yacht Utah, 60 Knightsbridge, London SW. ll, England Filed Feb. '7, 1961, Ser. No. 87,602 Claims priority, application Great Britain Feb. 25, 1960 3 fliaims. (Cl. 114-665) This invention relates to hydrofoils, or planing members for boats, aircraft and like vehicles, and has for its object to provide an improved hydrofoil system or stabiliser, for attachment to boats and the like, which will improve the riding performance of a boat or other vehicle moving in rough or undulating water.

Another object of the invention is to provide a stabiliser which will lift a boat rapidly to its hydrofoiling position on the boat getting under way.

A further object of the invention is to provide a stabiliser which is capable not only of reducing the surface area of the boat in contact with the water when under way, and thus improving the speed and performance of the boat, but also will automatically prevent a hydrofoil from having a negative lift on the boat encountering a wave, thu reducing porpoising and pitching in a boat equipped with the system.

A still further object of the invention is to provide an improved hydrofoil system which will eliminate or substantially reduce shock when the bow of the boat or the hydrofoil encounters a wave or re-enters the water after jumping out.

The stabiliser according to the invention normally operates at a relatively fixed inclination to the direction of motion of the boat, for example, the usual l /2, but automatically adjusts its inclination in accordance with relative vertical movement of the part of the boat to which it is attached, or on any change in upward loading on the stabiliser.

On the stabiliser becoming loaded, as for example, on the boat getting under way, or being further loaded, through being submerged, or further submerged in the water, as might happen on encountering a wave formation, or through the adjacent part of the boat dipping in the water, through pitching, porpoising, rolling or other uncontrolled movement, its inclination is automatically increased to raise the boat, and as the boat rises to its normal riding position, the inclination of the stabiliser becomes decreased toward its normal operating angle.

Stops are preferably provided to limit the amount of angular movement of the stabiliser, and these stops may be resilient to reduce the shock on rapid or severe changes in the inclination of the stabiliser during rough passages of the boat.

The hydrofoil and stabilising device, the subject of the invention has a main supporting hydrofoil, or planing member secured to a boat at a relatively fixed inclination to the direction of forward motion, and adapted to raise the boat when moving forwardly in Water. It has substantially rigidly associated therewith, or integral therewith, and above and in advance thereof, a sensing or probe hydrofoil, which is normally submerged when the boat is stationary, and is above the surface of the water when the boat is lifted normally during forward motion of the supporting hydrofoil. This sensing hydrofoil is adapted on encountering the water surface, either from above or below, to increase or decrease respectively, the inclination of the supporting hydrofoil relatively to the boat. The inclination of the stabiliser is thus adjusted automatically in relation to the nature of the water sur face encountered by the sensing hydrofoil and the passage of the boat is thereby smoothed out somewhat in rough or undulating water.

In one form of construction, the supporting hydrofoil comprises the lower portion of a substantially ellipticalsectioned tubular element arranged with its major axis horizontal, extending transversely of the boat, and the sensing hydrofoil comprises the upper portion thereof. The stabiliser is mounted for limited angular motion about a pivot within the tubular member, and extending transversely of its longitudinal axis.

The leading edge of the upper portion of the tubular element lies forwardly of the leading edge of the lower portion. The sensing hydrofoil portion is thus in advance of the supporting hydrofoil. The supporting hydrofoil is provided by substantially the whole lower half of the tubular element, and a somewhat di-hedral effect is obtained, since on the boat rolling, the larger lifting effect is thereby provided on the dipping side of the hydrofoil, and a corresponding smaller lifting effect on the other side, tending to produce a righting moment on the boat.

The tubular element can be of any suitable shape other than elliptical cross-section. For example, it can be circular, diamond-shaped, square or triangular, with the sloping sides meeting at the top or at the bot-tom of the stabiliser, according to the individual requirements of the boat to which it is to be affixed.

The material from which the tubular element can be constructed may be of uniform cross-section throughout, or it may be of aerofoil-section or have its leading edges curved upwardly, or thickened and rounded in section.

If desired, a flotsam deflector may be incorporated with the stabiliser. Such a deflector may take the form of a vertical fin, protruding forwardly of the stabiliser from within the tubular element. It may for example be a forwardly extending part of the vertical web portion of the stabiliser, or it may be attached to the said web, and have an upwardly inclined lower front portion, so that on striking flotsam, the supporting hydrofoil becomes into ride up and over the flotsam.

The invention is illustrated by way of example in the accompanying drawings, in which,

FIG. 1 shows in perspective a preferred form of construction of the stabiliser, and

FIG. 2 shows in side elevation a slightly modified form of the stabiliser.

Referring to FIG. 1 of the drawings, the stabiliser consists of an elliptical tubular element, 11, disposed with its major transverse axis extending horizontally, and trans versely of the boat. The tubular element is formed of a sheet of marine aluminum, or magnesium alloy; curved to elliptical tubular form with the end portions bent inwardly as shown, to form flanges 21 and 22, by which it is pivoted at 13 to a lug 14 depending from two outwardly flared flange plates 5 and 6, by which it may be secured on the underside of a boat hull.

Two stops 7 and 8 on the lug 14 limit the pivotal movement of the element to about 20 and rubber buffers 2 and 25 respectively on the stops 7 and 8 serve to cushion the element on reaching the extreme positions of its movement, and prevent jarring.

A vertically disposed web 32 extends from between the flanges 21 and 22 to the front part of the bottom portion of the tubular element to reinforce this latter and prevent flexing of the front of its bottom portion. This web may also serve as a flotsam guard which will rotate the stabiliser to raise the boat in the water on the guard striking flotsam.

A second web 33 may be provided at the rear end of the stabiiiser, depending from the flanges 21 and 22 at the rear, and terminating just short of the bottom por-- tion 11 of the element to limit upward flexing of its rear portion.

in the arrangement of the stabiliser shown in FIG. 2,

.9 the rubber buffers 26 and 27 for limiting the pivotal movement of the stabiliser extend between its downturned flanges and abut in the extreme positions of the stabiliser against portions 28 and 29 respectively of the lug 14. In this arrangement, an alternative form of flotsam guard is shown in chain dotted lines, 32'.

The lower portion 31 of the tubular element 11 constitutes the main supporting hydrofoil of the stabiliser, and the upper portion 17 constitutes the sensing hydrofoil.

The leading edge 30 of the tubular element is curved as shown in side elevation in FIG. 2, with its upper portion 17 lying forwardly of its lower portion 31.

In operation, the boat moves forwardly and gathers speed with the stabiliser submerged, and pressure on the sensing hydrofoil 17 tilts the stabiliser to a sharper angle of attack, causing it to rise steeply, and thus lift the prow of the boat out of the water. When the sensing hydrofoil 17 clears the water surface, the centre of pressure moves rearwardly to behind the pivot pin 13, so that the inclination of the supporting hydrofoil 31 decreases un til it resumes its normal position, about to the horizontal, with the heel portion against the stop 7 (FIG. 1), or with the stop 26 against the rear portion 20 of the lug 14, (FIG. 2). In this position the supporting hydrofoil 31 planes on the water surface with the sensing hydrofoil 17 clear of the water surface, until a wave formation is encountered. On entering a wave, the pressure of the water on the sensing hydrofoil 17 tilts the stabiliser to increase the inclination of the supporting hydrofoil 31. This causes the bow of the boat to be lifted until the sensing hydrofoil -17 is again clear of the water surface, when the supporting hydrofoil 31 will plane up the surface of the wave.

If the stabiliser encounters flotsam, the sensing hydrofoil 17 is again lifted and the supporting hydrofoil 31 actuated to lift the bow of the boat over the flotsam.

The stabiliser operates as a hydrofoil at speeds suited to hydrofoils, and as a skid or planing surface at the higher speeds, at which hydrofoils normally tend to produce cavitation.

The stabiliser may be attached to the rear end of a boat as well as to the front end. By having at least two stabilisers at one end of a boat, spaced apart laterally, and at least one at the other end, on reaching a sufficiently high speed, the boat-may be raised entirely out of the water, and will travel on the stabilisers operating as skids or planing surfaces.

I claim:

1. A hydrofoil and stabilising device for a boat, having a lower supporting hydrofoil and an upper sensing hydrofoil rigidly connected thereto and in advance thereof, a pivot secured on the underside of the boat hull and extending transversely between said hydrofoils, about which they are mounted for rotational movement, and stops on the device limiting such movement to about osa es 20, between the normal hydrofoiling position of the supporting hydrofoil and its maximum lifting position, in which device, the supporting hydrofoil constitutes the lower portion of a short tubular element rockably mounted about a transverse axis within the element, and the sensing hydrofoil constitutes the upper portion of said element, the leading edge of said upper portion lying forwardly of the leading edge of the lower portion.

2. A hydrofoil and stabilising device for a boat, hav- 0 ing a lower supporting hydrofoil and an upper sensing hydrofoil rigidly connected thereto and in advance thereof, a pivot secured on the underside of the boat hull and extending transversely between said hydrofoils, about which they are mounted for rotational movement, and

stops on the device limiting such movement to about between the normal hydrofoiling position of the supporting hydrofoil and its maximum lifting position, in which device, the supporting hydrofoil constitutes the lower portion of an elliptical shaped tubular member having 20 its major axi horizontal, and the sensing hydrofoil constitutes the upper portion of said member, the leading edge of said member being obliquely curved upwardly and forwardly so that the sensing hydrofoil is in advance of the main hydrofoil.

3. A hydrofoil and stabilising device for a boat, having a lower supporting hydrofoil and an upper sensing hydrofoil rigidly connected thereto and in advance thereof, a pivot secured on the underside of the boat hull and extending transversely between said hydrofoils, about which they are mounted for rotational movement, and stops on the device limiting such movement to about 20, between the normal hydrofoiling position of the supporting hydrofoil and its maximum lifting position, comprising a tubular element formed of sheet material curved to substantially elliptical shape with the upper ends of the sheet bent radially inwardly to form flanges through which the pivot passes, and the leading edge being curved obliquely forwardly, the lower portion of said element forming the supporting hydrofoil and the upper portion forming the sensing hydrofoil and extending forwardly of the leading edge of the main hydrofoil.

References Cited in the file of this patent UNITED STATES PATENTS 857,951 Meacham June 25, 1907 1,976,046 Tietjens Oct. 9, 1934 2,387,907 Hook Oct. 30, 1945 2,603,179 Gardiner July 15, 1952 2,972,974 Follett Feb. 28, 1961 FOREIGN PATENTS 582,985 Great Britain Dec. 4, 1946 436,203 Italy June 14, 1948 86,945 Norway Feb. 20, 1956 1,179,702 France Dec. 22, 1958 

1. A HYDROFOIL AND STABILISING DEVICE FOR A BOAT, HAVING A LOWER SUPPORTING HYDROFOIL AND AN UPPER SENSING HYDROFOIL RIGIDLY CONNECTED THERETO AND IN ADVANCE THEREOF, A PIVOT SECURED ON THE UNDERSIDE OF THE BOAT HULL AND EXTENDING TRANSVERSELY BETWEEN SAID HYDROFOILS, ABOUT WHICH THEY ARE MOUNTED FOR ROTATIONAL MOVEMENT, AND STOPS ON THE DEVICE LIMITING SUCH MOVEMENT TO ABOUT 20*, BETWEEN THE NORMAL HYDROFOILING POSITION OF THE SUPPORTING HYDROFOIL AND ITS MAXIMUM LIFTING POSITION, IN WHICH DEVICE, THE SUPPORTING HYDROFOIL CONSTITUTES THE LOWER PORTION OF A SHORT TUBULAR ELEMENT ROCKABLY MOUNTED ABOUT A TRANSVERSE AXIS WITHIN THE ELEMENT, AND THE SENSING HYDROFOIL CONSTITUTES THE UPPER PORTION OF SAID ELEMENT, THE LEADING EDGE OF SAID UPPER PORTION LYING FORWARDLY OF THE LEADING EDGE OF THE LOWER PORTION. 